1. The Field of the Invention
The present invention relates to devices for injecting a local anesthetic into the body of a patient for local infiltration, particularly for injecting a local anesthetic into very tough, dense ligamentary tissue surrounding a tooth or teeth prior to work by a dental practitioner (e.g., extraction of a tooth, cleaning of a root canal, or other procedure).
2. The Related Technology
Operative dentistry often requires local anesthesia prior to performing the procedure. More than half of the teeth in the oral cavity can be effectively anesthetized locally by infiltrating an anesthetic composition near the location of the tooth root apexes. Because of the pain associated with such procedures, it is desirable to first administer a topical anesthetic (e.g., benzocaine) adjacent the tooth followed by injection of a local anesthetic (e.g., lidocaine) to the tooth via local infiltration, an intraligamentary procedure, or by remote nerve block. For local infiltration and intraligamentary procedures, a small diameter needle is typically used. In recent years, it has been found that the smaller the diameter and sharper the point of the needle, the less painful is the resulting injection. Because of this, very small needles are sometimes used when administering a local anesthetic adjacent the base of a tooth prior to such work. Unfortunately, because of the very tough and dense nature of the ligamentary tissue into which the needle is pressed and the close proximity of the bone to the root surface, small diameter needles will often bend or “noodle” when attempting to push the needle into the tissue. In addition, as small as these needles are, they are nevertheless large enough to induce pain because of the rich supply of very sensitive nerves within the oral cavity. Although it might be thought that the use of even smaller needles might further reduce pain, the use of such needles is not practical because of their even greater tendency to bend upon attempting to push them through tough, dense tissue.
In addition, it can be very difficult to maintain the needle at a constant depth while attempting to inject the local anesthetic, as very high fluid pressures must be applied manually by the practitioner in order to effectively inject the anesthetic into the dense, tough ligamentary tissue. For example, fluid pressures of hundreds of pounds per square inch (“psi”) may be required during injection, which can make it very difficult to hold the needle steady and avoid pushing the needle further into the tissue, risking contact or penetration into the periosteum or bone covering adjacent the tooth root, which is very sensitive. Additionally, existing lever type injection syringes can be clumsy to align, and can easily cause rocking motions when delivering the anesthetic. Finally, they are relatively costly, particularly to clinicians practicing in third world countries.
In addition, current methods of injecting local anesthetic adjacent a tooth via local infiltration and conventional nerve blocks are rather complicated, requiring a significant amount of education and practice to perform them correctly and effectively. Some practitioners, particularly in third world countries, simply do not learn the techniques, but rather will perform a root canal, extraction, or other operative dental work without any anesthesia, which causes the procedure to be extremely painful from the perspective of the patient.
Therefore, what is needed is a needle device that can minimize pain during penetration into the tissue at the base of the tooth, but which will also minimize the tendency of the needle to bend or buckle during insertion as a result of the dense and tough nature of the ligamentary tissue. It would be a further advantage if such a needle device could be employed in simplified methods of applying local anesthesia so that practitioners could more easily learn and effectively utilize such a technique.